This thesis focuses on one semantic and one phonological factor that have separately been proven to have an influence on lexical access, both in speech perception and production. The factors are imageability, how easily a word gives rise to a mental sensory image, and phonological neighborhood density, how similar sounding words are, respectively.

A main goal of this thesis has been to see if there is an interaction between the two factors in speech production and perception, and if the two factors behave in a similar manner. Two informant groups were tested in a visual and auditory lexical decision task for perception and a picture naming task for production. One group consisted of three male subjects with an acquired, focal language disorder (aphasia), and the other group consisted of 30 neurologically healthy informants. The words they were tested on came from four different word groups: high imageability and high phonological neighborhood density (PND) words, high imageability and low PND words, low imageability and high PND words, and low imageability and low PND words. The informants were tested both on reaction time and accuracy.

To find the right words for testing I had to calculate the phonological neighborhood density for words that already had received imageability scores. This has been a rather large part of the work with this thesis, as there was no information about Norwegian words' phonological neighborhood density before I started this work.

Based on previous research the expected results would be that high imageability words would be recognized and produced faster than the low imageability ones. High PND words should follow the same pattern in production, but would be expected to have longer response latencies than low PND words in perception. The results from this study, however, show that imageability is the only factor that behaves according to the predictions. Phonological neighborhood density does not show any significant effects, nor is there any interaction between the two factors. There is a tendency, however, that high phonological neighborhood density slows down both perception and production of words, which is a quite unexpected finding, based on previous research. This might suggest that a word's imageability is a more important factor for lexical access than the phonological properties of the word. The informants with and without aphasia show similar patterns for the two tasks, which indicates that speech processing is controlled by the same mechanisms for speakers with and without acquired, focal language deficits.